Air cooling of the cylinders and pistons and other working parts of internal-combustion engines, compressors, and the like



March 22. 1927.

A. G. M. MKZHELL AIR 000mm OF THE CYLINDERS. AND PISTONS AND OTHER WORKING PARTS OF INTERNAL COMBUSTION ENGINES. COMPRESSORS, AND THE LIKE Filed June 29, 1925 3 Sheets-Sheet March 22. 1927. A. a. M. MICHELL 1,621,943

AIR COOLING OF THE CYLINDERS AND PISTONS AND OTHER WORKING PARTS OF INTERNAL COMBUSTION ENGINES. GOMPRESSORS AND THE LIKE Flled June 29, 192-3 3 Sheets-Sheet 2 March 22, 1927. j L 1,621,943

AIR COOLING OF THE CYLINDERS AND PISTONS AND OTHER WORKING PARTS GF TNTERNAL COMBUSTION ENGINES, COMPRBSSORS, AND THE LIKE Filed June 29. 1.923

3 Sheets-Sheet 3 Patented Mar. 22, 1927.

UNITED, STATES PATENT OFFICE.

ANTHONY GEORGE HALDON MICHELL, OF MELBOURNE, VICTORIA, AUSTRALIA, AS- SIGNOR TO ORANKLESS ENGINES (AUS) PROPRIETARY LIMITED, OF MELBOURNE HEISSUED AIR COOLING OF THE CYLINDERS AND PISTONS AND OTHER WORKING PARTS OF INTERNAL-COMBUSTION ENGINES, COMPRESSORS, AND THE LIKE.

AUSTRALIA.

Application filed June 2a, 1923, Serial No. 648,543, and in Australia Jul is, 1922.

The purpose of .the present invention is to secure more efiicient cooling by air currents of the; cylinders pistons and other working parts of machines operating with 5 hot working fluids particularly lnternal combustion engines the invention being also applicable to air and other compressors-1n which the working fluid is heated by compression.

1 It has been suggested heretofore to employ radiating fins in conjunction with a series of ducts communicating with the atmosphere and the channels between said fins whereby a plurality of air channels are rovided, fed continuously with fresh air the eed being created either by a fan or suction from the exhaust pressure of the engine.

In the suggestions hitherto advanced for carrying out this method of air cooling the essential factors governing the practical application of-same havenot been stated or enlarged upon with a view to ascertaining an eflicient arrangement of the air channels.

By this invention it is sought to achieve same and before proceeding to specify the im- Y rovements according'to this invention the ndamental considerations in the rational design of an air cooling system will be stated.

The tenor of the calculations is as follows The main data of the problem are: (A)

the quantity of heat which must be'dissipated per unlt time in order to maintain a steady temperature; (B) the area of surface .of the hot body which can be made available for conduction of heat to the air; (C) thedifierence .of temperature between the hot body and the air; (this difference being dependent on the temperature of the air, and the maximum permissiblesteady temperature of the cylinder or other hot body) (D) the permissible rate at which energy 'may be expended in moving the cooling air for the purpose of bringing it into contact with the body. (A), (B) and (C) jointly determine the velocity'with which air must be caused to flow over the surface of the body, the rate of conduction of heat being known to vary a proximately as the threefourths power 0 the velocity of the air. This velocity jointly with (D) determines the maximum quantity of air which can be circulated, and the latter quantity jointly with (A) determines a minimum increase of temperature which must be given to the current of cooling air. The ratio of such increase of tem erature to the initial difference between t e temperatures of the hot body and cooling air determines, from known experimental laws, the ratio of the transverse dimensions of the air channels to their effective length. By effective length of an air channel is meant its length in the direction of a stream of air from the place where the stream enters the channel to the place where it leaves.

The velocity and quantity of an, already assigned, jointly determine the total sectional area of these channels while their number and individual dimensions are settled by practical considerations as to economical processes of workmanship having regard .to the materials to be applied.

In this way, there are for each class of materials limitations to the appropriate transverse dimensions and efi'ective lengths of the air channels. For the best results it is usually desirable that the ratio of the effective length of the channel to its width should be of the order of 20 or 30 and a secure such a ratio without incurring difii-.

culties of construction. In the case of castiron c linders of ordinary dimensions and as or inarily constructed the appropriate channels are of comparativel large transverse dimensions and their effzctive lengths, deduced by the process outlined above, may be such that each channel extends throughout the length or circumference of thecylinder. In the case however of cylinders of forged steel or similar materials, such as are chiefly contemplated in-the resent design, the formation of such relatively large channels is very-wasteful and expensive, and channels of relatively small section being adopted, the process of calculation above explained requires the use of channels whose effective length is small in proportion to the length or circumference of the cylinder.

A leading purpose of the present invention is to provide modes of construction and arrangement of air-channels suitable I for forge cylinders of internal combustion engines and in accordance with the princlples above set forth.

As above stated the ratio of the effective length of such channels to their width or smaller transverse dimension, is of the order 'of 20 or 30. In the case of rectangular cylinders on the line G-G of Fig. 1.

Fig. 3 is a similar cross section on the line HH of Fig. 1.

Fig. 4 is a diagrammatic view of air channels and Fig. 5 is a relatively enlarged view showing details of one channel.

As shown in Figs. 1, 2 and 3 the cylinder 4 1, whose centre-line is YY, contains a piston 2, in the form of a thin cylinder closed by the end-piece 3, and diaphragm 4, the latter carrying the slipper-cup 5 and slipper 6. The latter makes contact with the swashplate or slant 7 fixed on the shaft 42 whose centre-line is In these features, and in its general modeof operation the engine is in accordance with Patent 1,409,057 of above cited. Usually several cylinders are arranged circumferentially around the shaft 42, being all equidistant from it. The cylinder 1, is fitted with exhaust valve 8, and induction valve 9, the latter being contained in an inductionbranch 10 connecting with the induction chamber 11, commun1cating with main induction pipe 12. The actuating mechanism of the valves the ignition apparatus and other accessories are not shown, the following description and the drawings being restricted to such matters as are necessary for the clear understanding of the nature of the invention, i. e. the improved means of air cooling.

The walls 13, 14 of the cylinder 1, and its combustion chamber, are formed as shown in Figs. .1 and 5 with relatively thin and deep circumferential fins 15, (a few only being shown in the drawings) forming between them narrow channels 15, the depth of these channels being-several times greater than their width. Surrounding these fins 15 is a mantle, comprising a thin shell 16 enclosing the fins, and an external jacket 17 the latter being formed in a number of segments either separate, as shown in Figs.

1, 2 and 3 or connected as shown diagrammaticall'y in Fig. 4. The shell 16 also may either be formed as shown as a separate piece or pieces, or may be made integral with the jacket segments 17. In either case the shell 16 is interrupted by a number of narrow longitudinal slots, 18, 18, these being alternately within and without the ducts 19, formed by the shell and the jackets 17 The slots 18 are open through the interspaces 18 between the jackets 17, to the atmosphere. The jackets and shell may be secured to the cylinder 1, by circumferential screwed bars 20, 21 with saddle-pieces 22 or other suitable means (see Fig. 2).

At the outer end of the cylinder the jacket ducts 19, merge into a common outlet consisting of a circular cowl or short pipe 23, coaxial with the cylinder 1, and surrounding the central exhaust valve 8. The wall 24 of this pipe is continuous circumferentially being formed as a continuation of the peripheral walls of the jackets 17. The interspaces 18 are closed at their outer ends by cross walls 25, so that no direct communication exists from the atmosphere into the pipe 23. The ducts 19 on the other hand terminate at the opposite or inner end of the cylinders, being preferably of continuously diminishing radial width in this direction whereby the velocity of the air past the whole of the slots 18 is maintained more or less uniform.

The exhaust valve 8, has its stem 8 and spring 28 supported in a cage 29, which is preferably integral with the ring 30 which forms the exhaust port, being united thereto by webs 31',and furnish with wings 32, (which may be formed as extensions of the webs) extending radially beyond the ring 30, into the path of the air flow from the ducts 19 and thereby acting as cooling fins for the exhaust valve casing 29. The spring 33 of the induction valve 9 is external to-the pipe 23 as shown (see Fig. 1.)

In order to draw an effective current of cooling air through the system of pipe 23, ducts 19, slots 18 and 18, and channels 15, a fan 35, having blades 36 may be employed. This fan may be mounted directly on the shaft 42, so as to be rotated thereby, and a shroud ring 37 and diaphragm plate 38 may be provided to enclose the pipes 23 of all the cylinders (arranged, as above indicated, in a circumferential series) and thus exclude all means of ingress of-air, other than that through the passages above mentioned from the atmosphere to the inlet side of the fan.

The action of the fan in inducing the desired current of air is assisted by the ejector action of the exhaust gases issuing from the ring 30, into the pipe 23, the action of these parts being similar to those of the exhaust nozzleand blast pipe of a steam locomotive.

efiective for this purpose, and by this arrangement a large dedution from the weight of the slant otherwise necessary may be made. In order to efi'ect cooling of the piston,

-which as above stated is preferably constructed as a thin cylinder and consequently inca able of transmitting heat at a sufficient rate y metallic conduction, it is made fluidtight by welding or otherwise hermetically joining the end piece 3, and diaphragm 4 to the cylindrical body, and a quantity of a suitable conductiveliquid, e. g. mercury is enclosed within it. A plug 41, is provided for introducing this liquid which is thrown from end to end of the hollow piston as the latter reciprocates, The end-piece 3 and dia hragm 4 are respectively made convex and concave on. their interior sides, so as to eifectively distribute the liquid over the surface of the former and of the cylindrical body of the piston as indicated by the dotted lines in Fig. 1.

The use of mercury in a hollow piston as a cooling agent has been practiced or proposed in connection with cylinders cooled byother methods, but the application of such cooling agent has 7 a special appropriateness and function in cooling the head of along cylindrical hollow piston of the form described, the heat being thus transferred from the head of the piston to its cylindrical wall, and thence to the corresponding wall of the cylinder, the latter being air-cooled throughout its length.

. I claim 1. In a cylinder cooled by circulation of air, multiple channels formed circumferentially around the cylinder and having each a plurality of lateral inlets alternating with a corresponding plurality of lateral outlets for the circulating air, each inlet and outlet slot common to a plurality of channels, the len th of each channel between inlet and outlet being many times greater than its smaller transverse dimension.

2. In a cylinden cooled by circulation of air, a plurality of circumferential fins forming between them narrow channels, and acylindrical shell enclosing the latter and in which is formed a plurality of narrow longitudinal inlet slots alternating with a corresponding plurality of narrow outlet slots each slot being common to substantially all the channels.

3. A cylinder to be air-cooled having a series of narrow circumferential channels formed thereon, longitudinal air ducts trans-.

verse to said channels, and a cylindrical covering shell formed with a seriesof longitudinal slots making communication between the channels and theair-ducts.

4. In a cylinder cooled, by circulation of air, a plurality of circumferential fins enclosing between them a corresponding plurality of narrow circumferential channels, and a cylindrical shell enclosingthe latter and in which is formed a plurality of narrow longitudinal inlet slots and a plurality of narrow lon itudinal outlet slots extending across the f ins, each of the latter opening laterally into a longitudinal duct conveying the air from such outlet,

5. Means for cooling a plurality of cylinders grouped circumferentlally with parallel axes, consisting of a plurality of mantles onclosing each of the cylinders, and through which the circulated air enters radially to each cylinder from the external atmosphere, and from which it is delivered longitudinally into a common outlet casing.

6. The combination of an engine e linder,

a plurality of circumferential fins orming channels surrounding the cylinders, a hollow jacket for the fins, having a plurality of longitudinal slots for admitting air to said channels, said jacket having longitudinal openings in its inner wall between. said slots to admit air to the interior of thejacket from said channels.

7. The combination of an engine cylinder, a plurality of circumferential fins forming channels surroundin the cylinders, a hollow jacket for the fins having a plurality of longitudinal slots extending across the fins for admitting air to said channels, said jacket having longitudinal openings in its inner wall between said slots to admit air to the interior of the jacket from saidchannels, means closing the longitudinal slots at one end, and an outlet casing communicat-' ing with the interior of the jacket.

8. The combination of an engine 0 linder,

a plurality of circumferential fins, orming channels surrounding the cylinders, a hollow jacket for the fins having a plurality of longitudinal slotseach for admittin air to all of said channels, said jacket having longitudinal openings in its inner wall between said slots to admit air to the interior of the jacket from said channels, means clos ing the longitudinal slots at one end, and an the interior of said jacket both slots extend- 1 ing across the fins, and an exhaust fan co- I a pipe common to the ducts, a fan, a shroud operating with the open end of said jacket.

10. The combination with an engine cylinder, of peripheral cooling fins thereon, a hollow jacket for said fins and having longitudinal entrance slots extending across the fins to supply air to said fins and alternate discharge slots opening into the interior of said jacket, the interior of said jacket constituting longitudinal ducts terminating at ring inclosing a chamber between-said cylinder and fan and an exhaust valve discharging into said chamber.

11. The combination with an engine cylinder having closely arranged cooling fins thereon; of a thin mantel surrounding said fins and provided with parallel longitudinal slots crossing the fins and a jacket having portions arranged between the slots in the mantels to form inlet slots for air said portions connected by cross walls, and a fan to exhaust one end of said jacket, whereby air will enter through the inlet slots into the narrow peripheral channels between said fins and pass only partially around the circumference of the cylinder between the fins, through the slots in the mantel into the interior of the jacket for exhaust by said fan in substantially separate currents.

12. The combination with an engine cylinder having closely arranged peripheral cooling fins thereon; of a thin mantle contacting with the edges of the fins and having longitudinal slots therein extending across the fins, a jacket surrounding the mantle having longitudinal slots also extending across the fins and chambers covering the slots in the mantle of considerably greater peripheral 4 Width than the slots in the mantles.

Dated this 25th day of May 1923.

ANTHONY GEORGE MALDON NllCiiELL. 

